White Film On Goldfish -5 Causes and Effective Treatment

It’s very normal to have several ailments in an aquarium.Among them, white film on goldfish is the most common. Generally, the white film is a protective slime that covers the entire body of goldfish.

Also, it is a secreted mucoprotein that actually fights against all possible fungal, bacterial, or parasitic diseases. Thus, the mucoprotein acts as a barrier that does not allow any infection to intrude inside the goldfish.

Unfortunately, the white film sometimes may act exactly the opposite due to several environmental issues inside the tank water. Then it becomes a problem. Sometimes, the film is predicted as white fungus.

However, the main reason for it is stress. What I’ve seen is, It can occur due to several reasons including water pH and other water parameters, fungal attacks, and others.

So, when the white film on goldfish becomes a problem, prompt treatment is necessary. Therefore, I am here to share all my experience with you to provide you with an easy and clear solution to this white film problem in your goldfish.

White Film on Goldfish – Symptoms They Show

Goldfish White Film

We have mentioned earlier that goldfish often have protective slime on them. But sometimes the slime becomes the reason for invading many bacteria, fungi, or ectoparasites. Thus, when it occurs, your goldfish start to show some unnatural symptoms. They are given below.

1. Excess Secretion of Mucus

This is one of the most visible symptoms that you will notice first. Excessive mucus secretion results in white patches over the fish skin and even eyes that looks like salt grains. It also causes gills inflammations.

2. Abnormal Behavior

It is also very visible. If you are an old pet keeper of goldfish then surely you are used to their behavior. Hence, any slightest change will make you worry and it happens when this problem arrives.

You will notice that the goldfish have lost their appetite or are swimming erratically around the tank water. Also, they are seen scratching against aquarium objects such as rocks, decorative pieces etc.

Moreover, you might also find them gasping at the water surface for air at the same time. You can also see them taking rapid breaths by opening and closing their mouth very frequently.

To some extent, the white fungus can intrude into the blood vein of the goldfish and cause a secondary infection. And once the secondary infection takes place there will not be any way to protect your goldfish.

3. Other Symptoms

There are some other distinct symptoms you may discover like discoloration, especially of the eyes and fins of the goldfish. Sometimes white, thread-like growth on the mouth, gills, or fins is also seen. Nonetheless, losing weight is also a symptom of this problem.

Why There Is White Film On My Goldfish

Causes of White Film On Goldfish

1. Stress

Sometimes everything seems perfect in your tank and suddenly you might find yourself asking what is this white film on your goldfish.Stress is probably the most possible reason why your goldfish is covered in a white film on them.

Once the aquarium goldfish is stressed out, they will not be able to secret mucoprotein that is healthy and protective.Rather than protecting the skin, the layer will sometimes become susceptible to several infections and parasite attacks when the fish is under stress.

Moreover, you might also find your goldfish is suffering from a parasitic attack at the same time. However, we have already said that there could be many reasons for stress. It could be environmental or even man-made.

Speaking of man-made situations, many aquarists want their aquarium to be filled with aquatic inhabitants and corals. But this idea is very wrong especially if you have already kept goldfish in it. Because they don’t like to be in an overcrowded aquarium at all.

Thus, high stocking density also increases the stress on goldfish and consequently leads them to secret white film instead of healthy mucoprotein.  

2. Water Quality

Water parameters and quality matter a lot to keep up a healthy environment inside the aquarium. This fact is also interrelated with the stress of goldfish. Poor water quality is one of the core reasons for stressing goldfish. It allows fungal growth inside the tank.

Moreover, poor water conditions are susceptible to parasitic growth as well. Warm water encourages bacterial growth. Thus, unstable temperatures cause poor conditions in the water. When the ammonia and nitrite and nitrate levels are high it creates a toxic environment for the goldfish. As a result, white film develops on their body.

Goldfish are coldwater loving so when the temperature goes above 75°F, sometimes they start secreting white substance from their body. Also, goldfish generally prefer a pH range between 6.5 and 7.5. So, fluctuations outside this range can cause stress to them and cause white fuzz in their body.

3. Excessive Chemical

The chemical presence that is more than necessary of course is a reason to form an unhealthy white film on goldfish. For example, excessive chloramine and chlorine in water also degrade the quality of water.

Also, if the tank water contains a high level of ammonia, then this might also cause problems for the goldfish. It blackens the skin of goldfish along with their fins.Moreover, the existence of lower oxygen saturation or higher levels of carbon dioxide elements also worsens the quality control of water.

This issue occurs when the tank is very crowded and the water is warm.All these chemicals that are mentioned above also cause severe stress to the goldfish which is also the main reason for developing a white film on them.

4. Fungal Infection

Fungal infection is another reason for creating a white film on goldfish. There could be several fungi that are sailing around the tank water like Dictyuchus, Achlya, or Saprolegnia. Wet and humid environmental conditions are favorable for their thriving.

Once the water conditions become favorable for the fungus they will reproduce in no time and attack the goldfish. Moreover, they cause fungal lesions on the fish skin leading them to death.

Then again, when the fungus is established, it quickly spreads and infects other animals in the tank as well. On the other hand bacterial infections in the goldfish can also cause slimy coat secretion that looks like a white film.

5. Problems in Diet

If you own goldfish, that means you have greater responsibility. They are high maintenance and require a proper diet. If anything is wrong with their diet or if the diet is contaminated, they may start producing toxic slime and hurt themselves.

Furthermore, improper diet leads to several other fungal diseases. It happens because if your goldfish do not like the food, they will not eat. Supply them high-quality fish food, mixed with fresh vegetables which will help the goldfish to prevent any kind of stress.

Therefore, the remaining food will rot eventually and and raise the ammonia and nitrite levels making the water contaminated. As a result the goldfish becomes more susceptible to fungal growth and their scales even can become white.

Treatment for White Film on Goldfish

Since the slime is suppose to be healthy but now it’s acting the opposite, your goldfish needs an immediate cure. The first thing we need to do is identify what is causing this white film on the goldfish. Examine your goldfish closely for any signs of illness, lesions, or abnormal behavior at first and try to go to the root of that.

Salt Bath

Salt Bath for Goldfish

If possible, isolate the affected goldfish in a quarantine tank. This helps prevent the potential spread of disease to other fish and allows for more focused treatment. You can try treating them with a salt bath.

You see, a salt bath can ensure a speed-up recovery when there is a mild symptom of the infection. However, many aquarists go for saltwater dips. Both of them are basically the same.

Nonetheless, this treatment is not that reliable. Yet, you can apply the method if you want a go-to solution.

However, to obtain this method, first, move your goldfish to a quarantine tank. After moving them to another water tank, add aquarium salt by maintaining the proper dose. You can buy aquarium salt in any nearby store. (Our Pick: API AQUARIUM SALT)

Mix one tablespoon of salt with one gallon of water. This ratio is suggested by professionals. Nonetheless, if the case is severe, you can add an extra pinch of aquarium soil. But also have to ensure that the salinity ranges between 10 ppt to 35 ppt. 

Moreover, make sure that the quarantine tank has the same pH, temperature, and water hardness. Also, do not let the fish take the salt bath for more than 20 minutes. Normally, let the goldfish stay there for around 2 to 20 minutes.

Luckily, goldfish are highly salt tolerant whereas other small fish are not that tolerant. Even most freshwater parasites and bacteria are also not salt tolerant. Some large fish, however, can tolerate salt baths.

Sometimes, you may notice goldfish are not tolerant anymore and they become distressed. As soon as you notice this symptom, remove the goldfish from the quarantine tank. You can also predict your goldfish are not on good terms when you see them rolling over or being distressed severely.


Sometimes skin disease like this is best treated with commercial medications. Medicine that contains formalin brings the best possible result in this case. Formalin works as the most active element.

Moreover, potassium permanganate and copper sulfate are also two active ingredients that help cure the infection in goldfish.

Nonetheless, if the infection goes to the secondary stage, then you might have to apply antibiotic medications. However, to attain the medication process, you have to isolate the goldfish first. It is essential since other animals in the aquarium might become affected.

Again, some antifungal medications will also help. Since goldfish are sensitive, Malachite green antifungal medicine will be helpful to fight the infection.

Furthermore, for severe cases, you can also consider methylene blue, gentian violet, or other effective antifungal solutions. However, make sure to carefully follow the instructions on the product to avoid overdosing the goldfish by accident. (Our Pick: De La Cruz Gentian Violet)

How to Prevent the White Flim Problem on Goldfish

Check your water conditions and maintain everything in optimal ranges to prevent this problem. You can use the master kit to measure the condition accurately. (Our Pick: API FRESHWATER MASTER TEST KIT)

Provide The Right Condition

Goldfish need plenty of space, about at least 30 gallons of aquarium volume per fish, to survive and thrive. When the tank is large, the water parameters are less likely to fluctuate.

So, this will protect them from many diseases as well. Ensure that the aquarium has adequate aeration and oxygenation

pH Range

If your aquarium contains goldfish then it is very important to maintain the pH. The pH condition of the tank water should be neutral. Thus, the pH should be from 6 to 7. However, goldfish can live spontaneously if the pH ranges from up to 8.5.

However, what goldfish do not like is the sudden change in water pH. An abrupt change in the pH can affect healthy slime production and lead them to produce an unhealthy white film.


Temperature is also important along with the water pH, to protect your goldfish. The optimum water temperatures for goldfish range between 55 to 80 degrees Fahrenheit. Lower or higher than the range can affect the goldfish adversely.

Nonetheless, surprisingly goldfish can live in little warm temperatures as well. But once the temperature gets more than 85 degrees Fahrenheit, goldfish cannot tolerate it anymore.

Moreover, higher temperatures create a breeding ground for parasites and fungi. Consequently, you will see the white fungus on the skin of your goldfish. So, make sure that you do not create favorable conditions for them.

No Chemical

The tank water should not contain any chemicals where you have kept the goldfish. Many times, aquarium water contains chloramine or chlorine in it. This chemical induces the secretion of white film in goldfish.

To remove chlorine from aquarium water, you can use de-chlorinator drops. Again, tap water also contains chlorine in it. Thus, if you are using tap water, then let the water rest for a couple of days. This way the chlorine will evaporate.

Clean the Waste

Not only goldfish but also any animal in an aquarium will produce waste. But if you let the waste float around the tank water, it will only encourage the production of several diseases. Hence, cleaning the waste on a regular basis is very important.

Moreover, the waste produces nitrates and ammonia in water. Both chemicals are very dangerous for goldfish. Therefore, perform water changes frequently to clean the waste and protect the goldfish.

Final Words

Now that you know why there is a white film on your goldfish, you also know what they are and what to do with them. Mucoprotein slime coat can turn into a dangerous substance for goldfish when they are stressed. Hence, maintenance of the slime coat is important.

Always keep a close eye on the affected goldfish during and after treatment and look for improvements in behavior, appetite, and the appearance of the white film.  It will help you to adjust the treatment based on your observations.

Also, know that prevention is always better than cure. Thus, try to make the aquarium environment safe for petting goldfish properly so that they don’t turn white. Soon, your fish slime will be restored back to normal. So, if our article was informative enough then let us know through your feedback. Also, we would love to answer your queries.

Howard Parker

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